1. Field of the Invention
The present invention relates to a method of producing an infrared image guide for use in instrumentation, medicine and the like.
2. Description of the Prior Art
The conventional infrared image guide has been produced by a method wherein a glass rod made of chalocogenide glass including arsenic sulfide and germanium sulfide, fluoride glass and the like is inserted into a synthetic resin tube, the resulting assembly being drawn under heating to produce an infrared fiber provided with a cladding formed of the synthetic resin tube around a glass core, and a plurality of such infrared fibers being adhesively bound in turn with tuning the arrangement phase of both ends thereof to each other.
It is, however, remarkably difficult to closely insert a glass rod into a synthetic resin tube. The generation of voids between the glass rod and the synthetic resin tube is inevitable. Thus, the conventional method had shown a disadvantage in that bubbles resulting from said voids are generated in the infrared fiber whereby the strength and optical characteristics of the infrared fiber are reduced.
In addition, the drawn infrared fiber per se has a remarkably small strength and the cladding is prone to be damaged, so that the operation for tying infrared fibers up in a bundle is inferior in productivity and besides, it is most difficult to exactly tune the phase of both ends of the infrared fibers, that is to say the larger the number of the infrared fibers is, the smaller the diameter of the core is, or the longer the infrared image guide is, the more difficult it is to tune the phase. It is not too much to say that only infrared image guides having a smaller number of bundled infrared fibers and a larger diameter of a core can be really produced.